#include<stdio.h>
#include<math.h>
int main()
{
	double n,a1=1.0,a2;
	scanf("%lf",&n);
	do
	{
		a2=a1;
		a1=(a2+n/a2)/2.0;
	}while(fabs(a1-a2)>=0.00001);
	printf("%.3lf\n",a1);
	return 0;
}
